Splay footed platform anchor



Aug. 18, 1970 l. POGONOWSKI SPLAY FOO'I'ED PLATFORM ANCHOR 2Sheets-Sheet 1 Filed June 27. 1968 Q a; i .EM l n; 0 i i 2 L x Z i x E 7Kw W M i M v t g- 13, 1970 l. c. POGONOWSKI 3,524,322

SPLAY FOOTED PLATFORM ANCHOR Filed June 2'7. 1968 2 Sheets-Sheet 2 1 .E.T /fl United States Patent 3,524,322 SPLAY FOOTED PLATFORM ANCHOR Ivo C.Pogonowski, Houston, Tex., assiguor to Texaco Inc., New York, N.Y., acorporation of Delaware Filed June 27, 1968, Ser. No. 740,585 Int. Cl.B63c 23/16; E02b 17/00 US. Cl. 6146.5 9 Claims ABSTRACT OF THEDISCLOSURE This invention relates to a marine drilling, and/or producingplatform for an offshore oil site. It relates in particular to such aplatform which, in normal operating position rests on the floor of abody of water and is there anchored by piling. The anchoring means takesthe shape of a splayed or spread pile arrangement to provide a more firmanchor, and stabilizing resistance against lateral storm forces.

Offshore drilling and production platforms should be designed today formaximum versatility. This feature would include not only the ability tobe readily moved between drilling sites but also the ability to functionproperly under adverse weather conditions and in varying ocean floorconditions. For example, the factor of weather by itself is pertinentsince stormy seas create not only surface turbulence but also largelateral forces. The latter is further aggravated by the activity ofperiodic tides and water currents peculiar to an area.

As the desirability for more exploratory and production work at deepwater sites increases, the complexity of drilling platforms increasescorrespondingly. Primarily, for deeper water the platform must possess agreater ability to withstand the above noted under water forces, but ofa greater magnitude. One inescapable factor is the widely diversecharacter of the anchoring media suggested by variations in compositionand consistency of the ocean floor at different locations. It is anaccepted assumption that varying soil and mud compositions requirevarying forms of pile arrangements to assure maximum platform holdingefficiency. Underconsolidated deltaic clay soils for example offer mostdifiicult anchoring conditions and ideally could support the structureagainst lateral forces by axially loaded heavily inclined pile to avoidexcessive bending.

For example the frictional retaining ability of a pile in a particularanchoring media will depend to a large extent on the pile length, or onthe area of contact be tween the pile surface and the anchoring media.Further, in the usual platform structure built by floating equipment itis customary to drive the anchoring piles into the ocean substratum at asubstantially vertical disposition. Often some slight digression from avertical holding arrangement is achieved by enclosing the piles withinhollow platform legs which are in turn directioned outwardly. In eitherinstance however the platform is fixed by a series of relatively uprightimbedded piles.

With such an arrangement, an inherent weakness persists, notably lateralwave and wind forces tend to rock or tilt the platform along one side ofthe base while tending to raise the opposite side from the ocean floor.This upward force exerts an axial pull on all of the anchor,- ing pilesin the base except those at the pivoting side. Were the anchoring pilesimbedded at an angle, particularly to form a flared arrangement aboutthe platform or any one leg rather than a vertical arrangement, overallholding ability would be greatly enhanced in soft soils. For example,the novel flared piling arrangement provides a stable holding means, andfurther in many underconsolidated floor consistencies the use of splayedor angularly imbedded piles suggests the only alternative to limitedability to penetrate the anchoring media.

To achieve a dispersed pile pattern in any offshore platform isvirtually impossible by use of presently known equipment. Normally, piledrivers whether barge or platform mounted, direct an imbedding forceagainst the pile in a generally vertical direction. To offset the hammermechanism from a vertical position for other than a vertical setting,tends to decrease the downward thrust because of frictional and otherlosses.

Toward overcoming the above stated problems there is presently discloseda unique and novel marine plat form for use at an offshore oil drillingor production site. The platform is adapted for firm anchoring orpositioning in a substream in such manner as to avoid displacement andtipping of the unit under severe weather conditions. The novel anchoringfeature is achieved by provisions of one or more support members whichafford lateral thrust reaction to the unit, said support members alsofunction to guide one or more piles from the lower end thereof into theocean floor.

The respective support members are disposed in an oblique relationshipto the upright and therefore direct the piles into the anchoring mediain a generally splayed or dispersed arrangement. Said support membersare normally under water and include an opening in the top side, adaptedto receive a mobile pile driving mechanism controlled or lowered fromthe water. surface, whereby the piles may be driven or imbedded byremote control.

It is among the objects of the invention then to provide a novel marineplatform adapted to be firmly anchored in the floor of a body of water.A further object is to pro vide a leg supported marine platform, thelegs of which include anchoring footings which extend at varying anglesinto the ocean floor. A still further object is to provide an anchoringarrangement of piles for an offshore platform wherein at least a portionof said piles are disposed in a splayed or spread arrangement to achievea firm grip on the substratum. FIG. 1 is a vertical elevation of amarine, oil drilling platform showing the novel pile footingarrangement. FIG. 2. is a sectional view of the platform shown in FIG.1, taken along line 22. FIG. 3 is a segmentary view on an enlarged scaleand in partial cross section, of a portion of the platform anchoringmeans shown in FIG. 1, and FIG. 4 is a cross section on an enlargedscale taken along lines 4-4 in FIG. 3.

An offshore platform 10 embodying a pile anchoring arrangement of thetype contemplated is shown in FIG. 1. This particular form of marineplatform is exemplary of, although not exclusive to the many typespresently known and employed wherein the novel anchoring means might beutilized. For the purpose of the following description, the marineplatform shown is of the monopod type consisting of a single uprightcolumn 11 which, when in a submerged position, extends substantiallyfrom the ocean floor to a point above the surface. A drilling orproduction deck 12 is fixed to the upper end of column 11 and ismaintained by under braces 13 and 14. Such deck or decks 12 are fittedto accommodate the normal drilling component of men, equipment andstorage facilities, including derrick 15 extending upward from the decksurface.

Deck 12 is normally elevated a predetermined height above the watersurface to permit an efficient operation and be beyond the reach ofwaves. To provide the platform with a degree of versatility therespective deck or decks are desirably removable from the platformwhereby A base 16 comprising footing elements 16, 21, 22 and 23respectively depends from the lower end of column 11 to provide anadequately wide seating surface which rests on the ocean floor. Thehorizontal span of base 16 is contingent to some extent on the height ofcolumn 11, but also on the consistency of the supporting substratum.Column 11 is preferably positioned concentrically with the base by lowerpiers 51, 52 and 53 to equally distribute loading stresses on thelatter.

A plurality of elongated, peripherally spaced support legs 17 and 18rigidize the column against external forces exerted against the columnsides both above and below the water. Such support legs enclose, and arenormally fastened to piles 19 and 20- which extend from the leg lowerend and are imbedded in the ocean substratum. The upper ends of therespective legs are spaced longitudinally along the column such thatpiles 19 and 20 enter the substratum at a slightly acute angle from anupright position.

As a matter of practicality, platform 10 in its entirety is constructedto be controllably buoyant and thus adaptable to be floated to adrilling position and submerged by controlled flooding. One embodimentof column 11 comprises essentially a uniform diameter cylindrical memberformed of end welded cylindrical steel rings. It is contemplated that amarine platform of the central column type is feasibly operable in waterdepths of between 150 and 1,000 feet. The column is therefore of anadequate cross sectional diameter with respect to its length, to assuremaximum rigidity at depths wherein the forces acting against the columnare greatly accentuated. While not presently shown, the column,following known practice, may include a plurality of conductor pipeswhich reach from the deck level to the ocean floor and accommodate theusual pipe strings for drilling and production purposes.

Column 11 may advantageously be constructed to embodying a plurality ofstrategically placed fluid tight tanks. The latter are interconnected toa control system of necessary pumps, valves, and manifolding to eitherstore oil pumped from the substratum, or to regulate the buoyancy andattitude of the platform in the water. This latter feature is of coursewell known and widely practiced in the art. However, in view of thediverse and specious equipment enclosed in column 11, passage throughthe column interior is virtually impossible.

Base 16, fixed at the column 11 lower end, includes a plurality ofmembers so constructed and fastened one to the other to assure theplatform a degree of stability when in a submerged position. Base 16 mayassume a variety of geometric configuration such as a triangular (FIG.2), square, or other, in achieving its intended purpose. In FIG. 2, base16 is seen to include at least 3 tubular conduits 21-23 inclusive,joined at the respective ends and welded to provide at least a part ofthe structure with water tight integrity. The tubular conduits aresubdivided into fluid tight compartments which, as in the instance ofthe column 11, are connected to a fluid control system such as pumps,manifolds and the like for regulating the fluid content of therespective tanks.

The primary purposes of the in-built tanks is two-fold. First, theyfunction as buoyant members in controllably regulating the attitude ofthe platform both at the water surface and during submerging of the sameto a predetermined position. A second feature of the tanks embodies thestorage of oil as it is removed from the substratum or alternativelyholding of water as ballast. However, the structural function of thebase is to assure the column being maintained vertically under alloperating conditions.

As above mentioned, normally the submerged column structure is subjectedto forces exerted by under water currents and also by conditions at thesurface. The latter is accounted for by storms and generally turbulentwaters which act against the column upper end and deck 12. Beneath thewater surface, currents and tides peculiar to the platforms environment,apply in effect, a discontinuous bending moment to the column whichvaries at different points of elevation in accordance with the water deth.

Io stabilize the upright column with respect to the base, and tominimize bending stress, legs 17 and 18 serve as terminal structuralelements, in both tension and compression, extending between the baseand the column upper end. A series of rigid intermediary members,otherwise defined as pile guides, comprise essentially elongated tubularelements fixed at the lower end to the base, and at the upper end tocolumn 11 outer wall.

These shorter intermediary members 42 and 43 for example extend betweenbase 16 and column 11. Said members are fixed at a lower elevation alongthe column than the legs 17 and 18. Similarly, additional intermediarymembers such as 51, 52 and 53 may extend from the column to the base atdifierent column elevations.

The purpose of these intermediate structural legs or pile guides is toboth rigidize the column against vertical bearing forces and alsoagainst bending forces due to environmental conditions. Referringspecifically to FIG. 3 each intermediary member or pile guide 42 isfixed at its lower end to a base member, and at the upper extremity tothe outer edge of column 11. The normal function of pile guide 42 is toretain a pile longitudinally therein until such time as the platform hasbeen submerged into place. Thereafter the pile is urged, while beingguided, into the substratum a predetermined depth to securely positionthe platform.

The splayed or spread disposition of the respective platform anchoringpoints is achieved by so placing the intermediary pile guides, as wellas the main legs 17 and 18 as to assume an angle from the vertical. Withthe respective pile guides fastened at different column heights, thepattern formed by the lower ends of the piles imbedded in the substratumwill be relatively flared or wide spread and consequently constitute aneflicient, versatile anchoring means.

Referring to FIG. 3, the lower end of pile guide 42 overhangs the base16 at the juncture of members 22 and 23. The guide pile lower ends maybe further provided with a cylindrical, detachably fastened sleeve 26.

Removable sleeve 26 is provided with a flange 27 at the inboard end,which flange engages a similar flange 28 at guide 42 lower end. Sleeve26 is rigidly engaged to guide 42 by a removable clamp 29, or by boltingdirectly through mating flanges 28 and 29. Sleeve 26 in essence definesa disposable rigidizing member between the centrally disposed pile 54,and guide tube 42. An annular space 56 formed between contiguoussurfaces of pile 54 and sleeve 26 houses a seal or collar 31. The lattercomprises spaced seal rings 32 and 33 disposed at opposite ends of thesleeve to form tight annular seals. In the usual manner a fluidizedmaterial such as cement or the like, which will harden to a rigid massis forced into annular space 56 between rings 32 and 33, therebyestablishing upon setting rigid connecting collar '31. Sleeve 26 isprovided with an inlet 36 connecting with line 37, the latter extendsupward to a source of fluidized cement or grouting at the water surface.A'second outlet 36 provided in sleeve 26 upper end is also communicatedwith annular space 56 for overflowing excessive grouting material afterthe collar space has been filled.

Pile guide 42, in the instance When but a single pile is to beaccommodated thereby, is provided as shown in FIG. 4, with positioningmeans such as a plurality of longitudinal bearing tracks 38, 39 and 41extending longitudinally of guide tube 42 and peripherally spaced tosupport and locate the pile 54. The latter is maintained substantiallyconcentric with guide tube 42 to insure proper alignment and rigidityduring insertion by the pile driving mechanism.

Guide tube 42 is structurally rigid and connected at one end to column11 to provide the column with necessary lateral support. As shown inFIG. 3 the upper end of guide 42 fastens to column 11 outer wall, beingfixed to the surface of the latter by welding or bolting as is mostfeasible. In an alternate arrangement, guide tube 42 may be connected bya column encircling collar or the like to engage the side of the column11 in providing the required lateral support.

In either structure, guide 42 is adapted at the upper end to receive amobile pile driving mechanism 46 shown in FIG. 3. The latter issupported from a cable 47 and lowered from the water surface either froma barge adjacent to deck 12, or directly from deck 12. Towardfacilitating operation of pile drive mechanism 46,: a guide system mightbe provided such as vertical tracks or taut cables extending from thewater surface to inlet 48 of the guide 42. Guide 42 is opened at thetop, defining inlet or aperture 48 of suflicient dimension to admit thepile driving mechanism 46. The latter upon entering the guide tubeengages bearing tracks 38, 39 and 41 thereby entering the legimmediately behind and in alignment with the upper end of pile 54.

Pile driving mechanism 46 comprises in essence standard drive apparatusadapted to facilitate mobility of the unit. The unit includes a mainbody, formed to re ceive a reciprocably moveable hammer or anvil 61. Thelatter includes a forward aligning and clamping head 62 which locks ontothe upper end of a pile to be driven. Remote activation of the hammer,where the latter is in place, thereafter causes the pile to becontrollably imbedded by the hammer impact a predetermined depth.

Pile mechanism 46 will of necessity be retracted periodically from pileguide 42 for the purpose of adding additional lengths of pile inaccordance with the consistency of the substratum into which the pile isbeing driven, and with the pile guide length. The pile is thus retainedwithin the guide tube by a locking or clamping mechanism duringtransportation of the platform and prior to being driven as desired.

At the drilling site, the platform is controllably submerged, or atleast partially submerged, by adjusting the buoyancy to bring base 16into position whereby the base resets upon the ocean floor oris in ahorizontal attitude. To initially fix or anchor the platform, pileswithin upright legs 17 and 18 are driven into the ocean substratum by aconventional pile driving mechanism either carried on deck 12 or on aderrick bai'ge positioned adjacent to the platform. Each of said legs 17and 18 may of course hold a plurality of piles as is customary, whichthen are disposed in a substantially upright position and driven intothe substratum a predetermined length in accordance with the soilconsistency and the expected operating conditions to which the platformwill be subjected. When so postured, the unit is lowered to contact theocean floor. Simultaneous with the setting of the main piles, thesupplementary or splayed footings comprising piles 54, 56, and 57 may beinserted. This is achieved by guiding mobile pile driving mechanism 46from the water surface to a submerged position, there to enter opening48 in the guide 42 top side, whereby the lowered end is guided intocontact with a pile upper end. The pile end, and drive unit 46 are thenlocked into a unit by remotely actuating the locking clamps 62.Thereafter, actuation of the driving mechanism causes the pile to beprogressed into the substratum.

In the instance of a relatively long pile length which exceeds thelength of the guide member 42, the pile as mentioned is elongated byremoval of driving mechanism 46 to permit the addition of pile lengthsto the pile upper end. The latter is achieved by welding the addedlength to the original length. The additional pile length may beinserted at the rear of guide 42 or through other convenient opening asin the guides upper side. In a similar manner, the added length may beguided to the original pile by access members formed in the guide uppersurface. Driving mechanism 46 is again inserted and the pile furtherdriven into the substratum. After reaching a prescribed anchoring depth,grouting material is directed to the sleeve 26 which long way of line37, and inlet 36, rigid connecting collar 34 between the pile and theguide tube.

- When at a subsequent date, it becomes necessary to move the platformto a different site, the latter is disengaged from its anchoring pilesin the usual manner. This consists of severing the pile by an explosivecharge or other means at a'point, near the ocean floor, whereby theplatform is freed. The latter is then free to be raisedto a floatingposition by controlled manipulation of the respective buoyancy tankswithin column 11 and base 16. In the surfacedfcondition, sleeve 26, isremoved from the respective guide tubes lower end thereby clearing thetube for the application of a new replaceable sleeve and the insertionof a new pile length. The platform is then ready to be floated to a newposition and again anchored.

Other modifications and variations of the invention, as hereinbeforeset'forth, may be made without departing from the spirit and scopethereof, and therefore only such limitations should be imposed as areindicated in the appended claims.

I claim:

1. In a marine platform for an offshore oil producing facility, saidplatform being adapted for partial submergence in a body of water and tobe fixedly anchored in the water substratum and derrick means adapted tocarry a mobile pile imbedding device;

(a) at least one support column disposed in a substantially uprightposition and extending from said ocean floor toward the water surface;

(b) elongated guide tube means having one end engaging said supportcolumn and having an open lower end disposed in a direction toward theocean floor;

(c) said guide tube means further including a guide passage adapted toreceive and position at least one anchoring pile, and to fixedly engagesaid at least one pile after the latter has been imbedded into the oceansubstratum from said guide tube open end; and

(d) means forming an aperture in said guide tube at a point spaced fromsaid open end, said means forming said aperture being sufiiciently largeto accommodate passage of pile imbedding device when the latter issupportably lowered form the water surface by said derrick means,whereby said imbedding device impacts said pile at the upper end forimbedding the same into said substratum.

2. In a marine platform as defined in claim 1, wherein: said elongatedguide tube means is disposed at an angle offset from an uprightdisposition.

3. In a marine platform as defined in claim 1, wherein; said elongatedguide tube means is disposed at an angle displaced downwardly from ahorizontal plane.

4. In a marine platform as defined in claim 1, including: a base lyingat a generally horizontal disposition and radiating outwardly from thelower end of said at least one support column, said elongated guide tubemeans including at least one rigid guide tube having an upper endthereof connected to said base thereby to laterally support said column.

'5. In a marine column as defined in claim 4, wherein: said elongatedguide tube means includes a plurality of guide tubes, each having theuppermost end thereof engaging said support column at spaced apartelevations along the latter.

6. In a marine column as defined in claim 1, wherein said guide tubemeans includes:

(a) at least one elongated guide tube,

(b) means in said guide tubefor retaining said pile therein duringembodiment of the latter into said substratum, and for fixing said pilein said guide tube subsequent to the latter be imbedded in saidsubstra-um.

7. In a marine platform for an offshore oil drilling and production sitebeing adapted for anchoring in the ocean floor and including;

(a) an elongated column disposed in a generally upright position andextending from the ocean floor to a position above the waters surfacesupportably carrying a deck above said surface;

(b) a base at the column lower end being normally resting in contactwith the ocean floor and having base elements spaced outwardly of saidcolumn;

(c) a plurality of rigid legs extending upwardly from said baseelements, the respective leg upper end being supportably connected tosaid column;

(d) pile guide means including a plurality of pile guide tubes, havingthe lower end connected to said base, and an upper end connected to saidcolumn at a point spaced downwardly from said elongated column upperend, and

(e) said plurality of pile guide including; at least one pile having aninboard portion rigidly connected thereto, said pile having an outboardportion imbedded in the ocean floor.

' 8. 'In a marine platform as defined in claim 7, including; a collarremovably connected to the lower end of said pile guide means and beingadapted to be firmly locked to a portion of a pile extendingtherethrough for positioning said pile with respect to said platform.

9. In a marine platform as defined in claim 7, including; a collarremovable positioned at the lower end of said pile guide means, saidcollar including a rigid joint between said collar and said pile wherebysaid pile is firmly locked to said guide means.

References Cited- UNITED STATES PATENTS 2,775,095 12/1956 Harris 61463,429,133 2/1969 Hauber 6l46.5

FOREIGN PATENTS- 1,020,555

